mogenson opened a new pull request #1075:
URL: https://github.com/apache/incubator-nuttx-apps/pull/1075
## Summary
Lua is a popular scripting language that is tailored towards embedding in
applications and embedded devices. This PR builds Lua as an NSH app. The
`apps/interpreters/lua/Makefile` does a few notable things:
- fetches and unpacks a source tarball from the Lua website
- sets defines to use the `readline` library for the Lua REPL
- adopts logic from `apps/builtin/Makefile` to generate headers for
including builtin Lua modules
To expand on the last point: Nuttx apps can include
`apps/interpreters/lua/LuaModule.mk` to register a C module with the Lua
interpreter. This makefile uses the `register` target to write entries to the
`apps/interpreters/lua/registry` directory. See `apps/examples/luamod_hello`
for an example of how to register a builtin Lua C module. The Lua source file
`linit.c` is excluded from the build in favor of `nuttx_linit.c`, which
optionally opens core Lua modules in addition to registered builtin modules.
Here's an example of a Lua script to blink an LED using the `userleds`
driver:
```lua
-- concatenate strings and print to NSH console
print("hello from " .. _VERSION)
-- open device driver, file is closed when leds is garbage collected
leds = io.open("/dev/userleds", "wb")
-- from 1 to 10, inclusive
for i = 1, 10 do -- lua convention is to start at 1
-- pack value into uint32_t and write to file
leds:write(string.pack("I", i % 2))
leds:flush()
-- run sleep command from NSH
os.execute("sleep 1")
end
```
Required defconfig:
```
CONFIG_INTERPRETERS_LUA=y
CONFIG_NSH_READLINE=y
CONFIG_READLINE_CMD_HISTORY=y
CONFIG_READLINE_TABCOMPLETION=y
CONFIG_SYSTEM_NSH=y
CONFIG_USERLED=y
CONFIG_USERLED_LOWER=y
```
For Lua bindings to the `userleds` `ioctl` interface, checkout this external
Lua C module: https://github.com/mogenson/lua_userleds
## Impact
No modifications to Nuttx are required and no changes outside of
`apps/interpreters` and `apps/examples` were made.
## Testing
Lua versions 5.2.0 through 5.4.4 have been tested successfully on a Teensy
4.1 board and MacOS/Linux with the NSH simulator config. Lua version 5.1 and
lower have a slightly different build setup that is incompatible with these
Makefiles.
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